“the great attractor”

1. “the great attractor” mia kumagai astr007.301 4.21.06

2. what is the great attractor? • a gravitational anomaly in intergalactic space at the center of the local supercluster which reveals the existence of a localized concentration of mass equivalent to tens of thousands of galaxies • observable by its effect on the motion of galaxies over a region hundreds of millions of lightyears across • these galaxies are all redshifted, in accordance with the Hubble Flow, indicating that they are receding relative to us and to each other, but the variations in their redshift are sufficient to reveal the existence of the anomaly

3. where is the Great Attractor? • discovered in 1986, it is located in the direction of the Hydra and Centaurus constellations • a group of astronomers known as the "Seven Samurai" (David Burstein, Roger Davies, Alan Dressler, Sandra Faber, Donald Lynden-Bell, Roberto J. Terlevich, and Gary Wegner) found that galaxies are very unevenly distributed in space, with galactic superclusters separated by incredibly huge voids of visible ordinary matter

4. what is the Great Attractor? • the Great Attractor is one such structure, a diffuse concentration of matter some 400 million light-years in size located around 250 million light-years away in the direction of the southern Constellation Centaurus, about seven degrees off the plane of the Milky Way -- at a redshift-distance of 4,350 kilometers (or around 2,700 miles) per second • a diffuse mass concentration 250 million light-years away but so large it pulls our own Milky Way Galaxy along with millions of others towards it

5. observing the Great Attractor • calculations indicate that ~1016 solar masses concentrated 65 Mpc away in the direction of Centaurus would account for this • detailed investigation of that region of the sky 10 times too little visible matter to account for this flow, again implying a dominant gravitational role for unseen or dark matter • thus the Great Attractor is certainly there (because we see its gravitational influence), but the major portion of the mass that must be there cannot be seen in our telescopes • attempts to further study the Great Attractor and other phenomena are hampered due to the line of sight obstruction by its location in the zone of avoidance (the part of the night sky obscured by the Milky Way galaxy)

6. the Great Attractor in fiction • the Great Attractor is an element of Stephen Baxter's Xeelee Sequence of novels • In the motion picture Men In Black, J (Will Smith) accidentally sends a small, shiny object flying and bouncing around MIB headquarters, causing a commotion. K (Tommy Lee Jones) explains to him that it was a gift from the Great Attractor, who thought it was "funny as hell.” • In Terry Pratchett’s Discworld series, Azrael, the cosmic representation of the Death of Universes, is known as the Great Attractor.

7. summary: • the Great Attractor is far bigger than a galaxy • the Great Attractor is a supercluster, or something even bigger • the gravity of the Great Attractor has been pulling the Milky Way in its direction - the motion of local galaxies indicated there was something massive out there that are pulling the Milky Way, the Andromeda Galaxy, and other nearby galaxies towards it • for a while, nobody could see what it was, because it lies behind the plane of our galaxy, meaning the gas and dust in our Galaxy obscures the light from the Great Attractor, and it is outshone by the stars and other objects in our Galaxy • x-ray observations with the ROSAT satellite then revealed that Abell 3627, a previously known cluster of galaxies, was much more massive than originally suspected, containing many more galaxies • optical astronomers had missed a great number of galaxies, because of the obscuration, but with hindsight (and with better observations), could spot many more galaxies. It is now thought that the Great Attractor is probably a supercluster, with Abell 3627 near its center

8. •http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/GtAttractor.html•http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/GtAttractor.html •http://csep10.phys.utk.edu/astr162/lect/gclusters/attractor.html •http://en.wikipedia.org/wiki/Great_Attractor • http://www.solstation.com/x-objects/greatatt.htm •http://cow.physics.wisc.edu/~ogelman/guide/gr8a/ sites referenced: